Process of treating vegetable fibers



Patented July 14, 1931 PATENT OFFICE THEODORE 1P. HAUGHEY, OF AC'COMAC, VIRGINIA PROCESS OF TREATING VEGETABLE FIBERS No Drawing.

The present invention relates to the treatment of vegetable fibers, such as fibers of flax, hemp, ramie, jute, pita, abaca, or the like, to prepare the same for spinning, and comprises a novel process by means of which an improved product is obtained in a relatively shorter time and with relatively less expense than in processes heretofore employed. The new process permits the recovery of the gum from the fiber in its natural state and thus further reduces the total cost of the process.

In general. the process is characterized by the use of extremely dilute chemical solutions which serve the double purpose of preventing injury to the fibers and of insurlng recovery of the gum in its natural state. The use of such dilute solutions is made possible by suitable control of pressure and vacuum conditions and by mechanical treatment. The process is also characterized by the use of low temperatures whereby considerable economy in fuel is efi'ected and the quality of the fiber is conserved.

An important feature of the invention 1s the method by which the ends of the fiber are so conditioned as to adapt the treated fiber for spinning on mechanical appliances now generally employed for spinning cotton, wool, worsted, etc., in the textile industry Without substantial change in such machinery. After preliminary de-wooding and de-seeding, such as may be effected in any well-known type of decorticating machlne, the resulting fiber is in reality bundles of individual fibrous elements. Such bundles, when treated by known processes are not rendered suitable for use in known spinning machinery. The feature of the present invention above referred to comprises the cutting of thesebundles into lengths suitable for spinning prior to any chemical treatment thereof. When the bundles are so cut, the

subsequent chemical and mechanical treatment of the present process causes the individual .fibrous elements to move relatively to each other in a manner to increase the total length of the bundle or ribbon of fiber and to thus render the ends thereof tapered Application filed May 16, 1930. Serial N0. 453,107.

or frayed and therefore adapted for use in a he spinning machinery.

Briefly the new process comprises decorticating, cutting, and treatment of the fibers under pressure in a dilute chemical solution, followed by reduction of the pressure to less than that of the atmosphere while violently agitating the solution by passage of air therethrough to cause the gums and resins to become readily separable from the fibers; the fibers being subsequently washed, treated with suitable solutions and finally dried, picked and baled. The advantages inherent in the process above broadly described will become apparent from the more specific description of the preferred process as applied, for example, to flax straw, which will now be given. It will be understood, however, that the following description is intended as illustrative only and is not to be taken as limiting the invention beyond the scope of the appended claims.

The flax straw as it comes in bundles from the field or from storage stacks is delivered to a combined threshing and decorticating machine of the usual type wherein the fiber is partially de-wooded and de-seeded. The fiber delivered from the decorticating' machine is then cut into lengths depending upon the particular use to which the finished article is to be put; the preferred lengths for cotton, woolen and worsted materials varying in the wellknown manner. If the fiber is to be used in linen machinery or to be twisted with rayon, where long fibers are desired, then the cutting of the material as it leaves the decorticating machine is eliminated, and the fiber maintained in bundles to preserve the strands. Except in this latter case, the cutting of the fiber is effected for the double purpose of obtaining strands of proper length and of insuring tapered or frayed ends .of the fiber bundles suitable for spinning requirements, as above pointed out.

The material after sired lengths is thoroughly washed in cold water. It is then placed in a closed vessel and treated with an extremely dilute solution of permanganate of potassium, the pressure on the solution being at the sametime 10c being cut in the deraised to from four to twenty pounds without application of heat. This treatment'renders the gum soluble and completes the dewooding and de-seeding of the fiber. "Various other chemical solutions could be employed instead of the permanganate solution. For example, dilute solutions of caustic potash, caustic soda or permanganates of other bases have been found suitable, or saponifying or sulfonating oils such as castor, olive, linseed, soya, cottonseed, etc., or distillates such as alcohol, glycerine, or the like could be employed; the choice of chemical depending to a certain extent upon the type of fibers being treated and upon the age thereof. The strength of solutions of any of the chemicals above enumerated should preferably be about one part of the chemical to two hundred to eight hundred parts of water by weight, depending upon the reagent employed.

The digestion under pressure is continued for a variable length of time depending upon the particular material being treated and upon the dilution of the chemical solution employed. In general, not longer than forty minutes is required for this treatment and a considerably shorter period will be, in most cases, sufiicient. The pressure in the vessel is then reduced and a vacuum applied while air is introduced at the bottom of the vessel to cause violent agitation of the solu tion and loosening of the remaining shives, which, with the gum, rise to the surface of the solution in foamy bubbles under the influence of the applied vacuum and the circulating current of air. As: fast as the foam containing shive and gum rises to the surface, it is removed by the vacuum. After about ten minutes, or a shorter period of time,

has rendered the fiber practically free when the solution becomes clear, heated water of a temperature'preferably less than 180 degrees F. is introduced at the bottom of the vessel and passed upward through the fibers until the last traces of the chemical solution, shives and gum are removed from the fibers; the heated water carrying the imfrom the top of the The above treatment from extraneous substances and coloring matter and the a 'tation has insured the tapering or fraying of the ends of the cut fiber bundles.

The solution carrying the gums, shive and foreign matter is delivered to a separate container in which the gums are allowed to settle and the foreign floating material is removed from the surface of the solution. The gums may then be recovered in any well known manner, as by means of a centrifugal separator. The original chemical solution having been of such a very dilute nature, the gums will be found to be still in their natural form, and hence to be particularly suitable for recovery as a by-product.

The fibers, after the above treatment are purities being removed vessel by the vacuum.

screened by passage on a perforated conveyor and are then passed through squeezing rolls to remove water not drained therefrom during passage along the conveyor; the fiber being scraped from the conveyor to the rolls. The fiber is then put into a mechanical beater, and if any traces of the dilute chemical solution still remain, a dilute solution of' oxalic, sulphurous, phosphoric or acetic acid may be added to complete the conditioning of the ends of the fiber and to remove any traces of the chemical solution. The strength of this souring solution is preferably about one part of the acid to 600 to 1000-parts of water by weight. After a suitable length of time for the treatment of the fiber in the souring solution, the solution is drawn OE and a very dilute silk softener, such as vestasal, vitasal, serisal, or the like added, about one part of the softener to 400 to 700 parts of water. The fiber at this stage of the treatment will be found to be substantially bleached or whitened. If, however, further bleaching is found desirable, chlorine water may be added to the wash water in the beater in such quantities as may be found necessary for the fiber to acquire the proper degree of whiteness.

The fiber may now be removed from the beater and put through squeezing rolls to drain the water therefrom, and then passed directly to a mechanical picker. If a blast of warm air is directed on to the fiber during the picking thereof, it is found that the use of a drier is not essential, as such warm air blast sufiiciently dries the fiber for baling for shipment to the spinner.

If the fibers rayon manufacture or in linen machinery, the cutting of the fibers into suit-able lengths after treatment in the decorticating machine is eliminated, as is also the treatment in the beater washer. The entire treatment in dilute degumming, souring and softening solutions, and the washing of the fibers is effected while the fibers are in the digester and with the fibers carefully tied in bundles and the strands kept straight on frames. Although the above described treatment for the longer fibers involves a certain amount of manual labor in arranging the fibers and tying the ends thereof, it is found that the type of fiber result-ing is so greatly superior for the particular purpose desired, that the additional labor involved is well worth while.

It will be noticed that the above described process eliminates theprocess of retting which is ordinarily solaborious and so expensive. The gums and woody matter of the fiber are removed in a relatively short time and the' to be treated are tobe used in stantially pure cellulose, and is considerably stronger than fiber resulting from heretofore known processes for the treatment of bast fiber. It is believed that this is due to the use of such extremely dilute solutions whereby the original strength of the material is not impaired. The use of such dilute solutions is made possible by the use of pressure and vacuum conditions which conditions also serve to considerably shorten the period of time necessary for the entire process. It is believed that the forced circulation of air provided during the application of vacuum to the upper surface of the solution produces a partial and controlled oxidation which materially assists in the separation of the. wood matter and other impurities, and as sists t e degumming rooss by increasing the solvent action of the ath.

The following is claimed: 1. The process of treating vegetable'fibers which includes digesting the fibers in a' weak chemical solution under super-atmospheric pressure conditions to separate the gum and foreign matter from the fibers and thereafter treating the same under sub-atmospheric pressure conditions while forcing air therethrough to agitate the solution and to permit the removal of the gums and shive therefrom.

2. Steps in the process of treating fibers of flax, hemp or the like, which comprise'decorticating the fibers and then cutting the same in lengths suitable for spinning, followed by washing and digestion thereof under superatmospheric pressure in a dilute solution adapted to dissolve the gum and to separate the remaining foreign matter.

3. The process of treating vegetable fibers which includes digesting the fibers under pressure in a dilute solution adapted to dissolve the um and to remove the foreign matter and t en removing the gum under vacuum condition while agitating the solution by passage of air therethrough and finally treating the separated fibers with souring and softening solutions and drying and baling the fibers.

- 4. The process according to claim 3 wherein the gum is recovered by centrifuging the solution separated from the fibers.

5 The process of treating fibers of flax, hemp, or' the like which comprises digesting decorticated and cut fibers in a dilute chemical solution under a pressure of about ten pounds and thereafter reducing the pressure below that of the atmosphere.

6. The process of treating fibers of flax,

hemp, or the like, to producecellulose therefrom whlch includes digesting partially de-' corticated fibers under pressure 1n a dilute chemical solution adapted to dissolve the gum, removing the dissolved gum, washing the remaining fibers in warm water and thereafter treating the fibers with a dilute acid solution.

7. The process of treating fibers of flax, hemp, or the like, which includes cutting partially decorticated fibers into lengths suitable for spinning, digesting the cut fibers lently agitating the fibers while reducing the pressure upon the solution, and finally beating the fiber in souring and softening solutions.

y 9. A fiber treating process which includes I partially decorticatmg raw' fibers, cutting the same in lengths suitable' for spinning, and subsequently subjectingtthe'fibers to degumming, souring and so 10. A fiber treating process which includes cutting partially decorticatedfibers into lengths suitable for spinning and thereafter violently agitating the cut. fibers in a dilute solution of p'ermanganate'of potassium.

11. In a fiber treating process the method of preparing fiber of desired length with suitable ends'for spinning which comprises partially decorticating the untreated bers, cutting the same to a desired length for spinning, washing the cut fibers in cold water, digesting the washed fibers under pressure without additional heat in a dilute chemical degumming solution and thereafter reducing the pressure below atmosphere and agitating the fibers by forced circulation of air through the solution to produce suitable tapered ends ofthe fibers for spinning.

12. In a fiber treatin process according to claim 11, the metho gum in its natural state from the fibers which comprises withdrawing the diluted chemical I solution from the fibers and separating the v gum therefrom by centrifuging.

In testimony whereof, I have signed my name to this specification. 1

THEODORE P. HAUGHEY.

of recovering the ening solutions. l 

